


all night long

by Sin_Cognito



Category: Undertale (Video Game)
Genre: M/M, Smut, aphrodisiac, date, heatisiac, horny skeleton
Language: English
Status: Completed
Published: 2017-11-08
Updated: 2017-11-08
Packaged: 2019-01-31 02:29:42
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,395
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12666426
Author URL: https://archiveofourown.org/users/Sin_Cognito/pseuds/Sin_Cognito
Summary: Sans has planned the most perfect date for his brother and lover Papyrus. Everything has been thought thoroughly. Even a way to get round their little... predicament.





	all night long

**Author's Note:**

> From a kinktober prompt : Classic fontcest with aphrodisiacs? I'm not sure how it'd be portrayed with a picture... So, a fic~
> 
> Wow sorry this took so long ! I rewrote it several times and then just gave up on trying to write something good, but surprisingly it ended up not bad ? And also FINALLY SOME SMUT. Oh well.
> 
> today's new word is : shoot the breeze. Did I use it correctly ?
> 
> For those who aren't familiar with heatisiac, I'll just copy-paste the explainations from my kustard fic : heatisiac reduces a monster to a heat-like state, it lasts as long as a real one, but isn’t as dangerous if you choose not to do anything. It eventually wears off, while a real heat would just worsens if you don’t “treat” it. Also heatisiac doesn’t increases the odds of getting pregnant as a heat does.

Sans took another sip of his drink. It wasn't a very good idea, he had drunk a lot tonight already. WAY more than usual. But it wasn't the dizziness of the alcohol he was wary of. After all, how could one get tipsy when there was not a single drop of alcohol left in their drink ?

He lifted his head up and his eyes met the sun. Or more accurately his brother. Papyrus was smiling at him, his smile shining brighter than any star. Oh boy, sometimes Sans would forget how lucky he was to be dating the most perfect monster in the universe. But then a simple look at his sibling's shimmering eyes would bring him back to reality. To put it bluntly, he was in love with Papyrus. And he was the happiest monster in the Underground because Papyrus had chosen him to be his mate. Why Papyrus had chosen him was still beyond him though.

"how did you like your day Papyrus ?"

"It's perfect Sans. Just like you." The tall skeleton replied, making the older brother blush his signature blue magic.

The first part of their date had gone very well in Sans' opinion. He had planned it for several weeks and was relieved to hear Papyrus was enjoying it as much as him. It had started this morning by Sans accompanying Papyrus to his training with Undyne. The older brother knew the other needed his daily dose of exercise, but that was one thing he just couldn't help him with. So he decided if he couldn't help him, he would go there and cheer him with everything he had. And for a lazy monster, he actually had a lot in him. So Sans had basically spent all morning shouting praises and encouragements and wiggling cheering signs. He knew very well he looked goofy, but Papyrus just loved this kind of attention, and today was about pleasing his most precious baby brother.

After the workout at Undyne's, they both needed a warm shower. Or rather a warm bath in this case. They took their time soaking together in the tub, scrubing the sweat form each other's bones. The scrubing slowly dissolved into light kisses and gentle nibbles, which in turn dissolved into not so light make outs and heated nips...

Once they were dry and changed into proper date outfits, they headed for waterfall. Despite Papyrus going through the area everyday, since Undyne lived there, Sans was way more familiar with secrets hideouts and hidden spots that were perfect for the two lovers' date. He guided them to one of his favorite place : it was recluded enough not to be interrupted by strangers walking by, but close enough to the main path for echo flowers to be blooming. The natural blue lights of the cavern offered enough brightness to see, but were dimmer there and that was precisely why Sans loved this place : you could clearly see the stars. Not the real ones of course, but it was better than the shimmering rocks you could find in the rest of the cavern. The darker ceiling here concealed the rocks' shapes and made them look like twinkling stars in the night sky. Sans and Papyrus picniced and spent the afternoon there, quietly enjoying each other's company.

When the time for the main event came by, the two skeletons decided they didn't need to change again and went straight to MTT resort, where Sans had reserved the best table in the restaurant. It was very difficult to reserve even the most basic table in the high-end place and the older brother had had to pull some strings and go to great lenghs to reserve the spot. Only the best of the best for the Great Papyrus ! Of course, Sans had some trick up his sleeve, like he always did. He himself worked in the prestigious hotel so it was easier for him to reserve a good table. He had requested a private appointment with the ever busy Mettaton to ask a favor from the most famous robot of the Underground. After a bit of negociations (which ended up with Sans signing a contract to work for free for one month to make up for the demand) Sans obtained to have the best table reserved with a special 5-course meal and he could choose the background music for the duration of his date. Perfect.

He also obtained to be served a special drink that wasn't on the menu, but Papyrus didn't have to know about this particular favor...

Now that he thought about it, getting to see the pure bliss in Papyrus' gaze upon entering the grandiose hotel was totally worth working for free for a whole month. Sans knew how moved his brother was by the unusual lack of chit chat from the other. Sans had guided Papyrus to _the_ table before pretexting going to the bathroom and leaving the hall to get ready for yet another surprise. He went backstage and after reading his script once more to get in the mood for his comedy show, he placed himself in the center of the stage. The curtains rose and he began reciting his best puns and jokes. He had worked on this particular one-monster show for months now, writing jokes after jokes until the lines were perfect, until even Papyrus, who usually disapproved his dumb puns, wouldn't be able to stop himself from laughing. And sure enough, after a quick glance at their table, he could see his brother... laughing wasn't the word to describe the spasms of laughter shaking the other's body. Even from the stage Sans could see Papyrus having a fit of the giggles, occasionally wiping his crying eyes with the luxury napkin. _nailed it sansy_

After the show was over, he went back to their table and was welcomed by one of Papyrus' famous rib-crushing hug. He hugged his brother back and kept his larger hand into his tiny one when they sat down. Their pre-diner drinks came, a large starfait for Papyrus and his special drink for Sans. They ordered their food as well and began shooting the breeze while sipping their respective drinks.

By the end of his first glass, Sans knew he had miscalculated the quantities. HUGELY miscalculated. They were hardly into the first meal that he could already feel the effects of the drug he had asked the waiter to put in each one of his pre-paid 7 glasses. He had thought that drinking slowly and throughout the meal would reagulate the substance enough for him to hold until they got home. He had thought that blending half a cup of spider cider to the drug would lessen the immediate effects. Apparently he was wrong.

Heatisiac truly was a POWERFUL drug.

Sans didn't toy with the product very often, but he wanted today to be perfect for Papyrus. Papyrus who had an unfathomable sex drive. He was just too... willing for Sans. He could go on for hours and hours and Sans just couldn't keep up. His body was weaker and Sans was completely spent up after only two rounds. They couldn't really do anything about it so they usually tried to make the foreplay last as long as possible but even with that, Papyrus often had to stop before his thirst was entirely quenched. He never complained about it, of course he wouldn't, because he knew that it wasn't Sans' fault or anything. Yet the little skeleton couldn't help but feel bad for his precious little brother, who only deserved the best. So when he came across heatisiac, he found in the substance the perfect medicine for their trouble. He had thus decided to drink heatisiac all diner long (with a bit of spider cider added to the mix, for good measure) so that he would be able to... keep company to Papyrus tonight. Alas he had miscalculated the quantities and ended up horny as hell after only one drink.

His need for physical contact hadn't lessened in any way even after the last course. The two skeletons were now enjoying the last bits of their dessert and after the 7 drinks, Sans' whole body was druming with pent-up magic, deafening all his senses which alas sharpened his perception of his one true love, who was happily smiling accross the table, blissfully unaware of the torment he was putting Sans through. With every breath in, he felt his magic dropping to his nether regions, desperately trying to take shape. And yet he would deny them (or rather him in this case) the pleasure every single time. Everything today had been for Papyrus. It wouldn't do to spoil his last surprise now.

Thankfully Papyrus finished his treat and declared he was ready to go home. Sans agreed and without further ado they were out of the glittery restaurant. The walk through Hotland seemed interminable, the hot air like frozen bites accross Sans' heated bones. They had decided to go back home with the river-person, but even the small distance to the dock had been a never-ending journey for the little skeleton. And even on the boat there had been no respite with how their bodies swayed and bumped into each other with each wave.

"almost almost" Sans thought repeatedly, like a mantra.

Finally, the quiet lights of Snowdin came into view and Sans sighed in relief. Which proved to be quite short-lived as his body shook from a shiver. The cold air of Snowdin may have seemed better than Hotland, but the constant shivering of his bones only amplified the friction between his short and his crotch, increasing the risks of him forming ectoparts right there, in the middle of the road.

" _almost almost_ " his soul screamed.

  
"SANS WHAT'S WRONG ? WHY DID YOU STOP WALKING ?"

_because i was this close to forming ectojunk in front of the towns folks but everythings fine dont worry_

"nothin Paps im just... tipsy".

_yeah... tipsy..._

Bad move. With that, Papyrus grabbed his hand and dragged him forward, declaring Sans didn't need to know where he was going for the Great Papyrus would always show him the right way. Sans whispered a strangled "thankyou" but honestly all he could do now was focus on how warm and soft Papyrus' fingers were under the glove. He wanted... no he NEEDED those delicate fingers to touch him. To touch his body. Everywhere. Inside him. Right now.

The mental image of Papyrus wrecking him provoked another tremor in his magic.

" _ALMOST ALM-_

As soon as their frontdoor opened, Sans was on Papyrus, his lips on the other's mouth and his tongue inside, caressing hungrily the magic appendage. In his heated state he hadn't even realised they were already home. But he couldn't care less now that his arms were firmly locked around Papyrus' neck and his groin was finally, FINALLY, getting the long-awaited friction it so desperately needed. It took no time at all for his magic to form a cyan glistening pussy, already wet and litteraly dripping with desire. Even through his hazed mind, Sans was aware that only one pussy to play with wouldn't be enough for the two of them so he immediately set out on finding it a friend, namely Papyrus' perfect dick. He had already unbuttoned the other's dress pants when his hands were stopped.

"SANS, WHAT ARE YOU- AH !"

If his hands were unusable, he'd just stimulate the other's bones with his tongue. He lapped and licked Papyrus' pelvis like his life depended on it, until he felt the sweet taste of his brother's magic on his tongue. Drawing back slightly to let it take shape, he couldn't refrain a loud moan when he finally saw the orange dick manifest in front of him. He wasted no time in sucking the appendage, drawing delicious sounds from the taller skeleton. Papyrus finally let go of his hands, allowing Sans to grip the other's bones and push the dick even deeper in his mouth. The rod slid so perfectly against his conjured throat he just wanted to swallow the entire thing. He could taste his brother's precum on his tongue, the flavor tastier than any 5-course meal he could've eaten. Between two moans, Papyrus managed to put his hands on the back of Sans' skull, effectively speeding the back and forth of the little skeleton's cranium.

"S-Sans... aaah... It feels so good.... nnh-HH ! YES ! YES ! KEEP GOING !"

_anything for you bro_

"AAH SANS ! I'M GONNA CUM ! I'M GONNA-"

Just when he felt papyrus was about to burst his load, Sans quickly (and with great difficulties) drew back, eliciting a surprised and very frustrated cry from Papyrus. He knew this was an unfair move from his part, but he would be sure to make up for it very soon. He laid back and got rid of his annoying shorts, revealing his magic entrance to an enthralled audience. He spread his legs wide open and reached his pussy with his little hand, his fingers brushing past the sensitive magic to open the ecto lips. He offered himself to Papyrus.

"p-leaaase bro... in-side... aaah... meee..."

Despite his slurred speech, the message seemed to have reached Papyrus, who burried himself deep inside Sans in mere seconds. They both whined from the pleasure of their entertwined magic. Papyrus captured Sans' mouth in a heated kiss, swallowing his moans and making an utter mess of his blue tongue. The little skeleton gripped the fabric of the other's dress shirt in a desperate attempt at grounding into reality. The power of Papyrus' thrusts unbalanced him, and it didn't take long for Sans to feel himself tip over the edge. He came with a silent cry, his body tensing around Papyrus' cock. Seeing his older brother's face contort itself in pleasure was the final push for Papyrus, who blew his load inside Sans' blue magic. He kept on pounding into the small skeleton until he was thoroughly milked dry.

By the time Papyrus stopped his thrusts, Sans could already feel himself be turned on again.

Heatisiac was a powerful drug indeed.

"Aaah... Thank you Sans, that was... absolutely perfect," Papyrus whispered in a light kiss. "Now let's go shower, I feel sticky."

"are you kidding. i didnt drink 1.5 litter of heatisiac for you to only fuck me once. i can go all night bro."

"Oh."


End file.
